diff --git a/src/gps/RTC.cpp b/src/gps/RTC.cpp
index 9053f5b2b..e04f903ee 100644
--- a/src/gps/RTC.cpp
+++ b/src/gps/RTC.cpp
@@ -44,7 +44,11 @@ void readFromRTC()
     if(rtc_found == PCF8563_RTC) {
         uint32_t now = millis();
         PCF8563_Class rtc;
+#ifdef RTC_USE_WIRE1
+        rtc.begin(Wire1);
+#else
         rtc.begin();
+#endif
         auto tc = rtc.getDateTime();
         tm t;
         t.tm_year = tc.year - 1900;
@@ -110,7 +114,11 @@ bool perhapsSetRTC(RTCQuality q, const struct timeval *tv)
 #elif defined(PCF8563_RTC)
         if(rtc_found == PCF8563_RTC) {
             PCF8563_Class rtc;
-            rtc.begin();
+#ifdef RTC_USE_WIRE1
+        rtc.begin(Wire1);
+#else
+        rtc.begin();
+#endif
             tm *t = localtime(&tv->tv_sec);
             rtc.setDateTime(t->tm_year + 1900, t->tm_mon + 1, t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec);
             DEBUG_MSG("PCF8563_RTC setDateTime %02d-%02d-%02d %02d:%02d:%02d %ld\n", t->tm_year + 1900, t->tm_mon + 1, t->tm_mday, t->tm_hour, t->tm_min, t->tm_sec, tv->tv_sec);
diff --git a/src/main.cpp b/src/main.cpp
index d4d76cc3b..f9a475af0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -246,6 +246,13 @@ void setup()
     // In T-Beam-S3-core, the I2C device cannot be scanned before power initialization, otherwise the device will be stuck
     if ((HW_VENDOR != HardwareModel_LILYGO_TBEAM_S3_CORE)) {
         scanI2Cdevice();
+    }else{
+        // PCF8563 RTC in tbeam-s3 uses Wire1 to share I2C bus
+        Wire1.beginTransmission(PCF8563_RTC);
+        if (Wire1.endTransmission() == 0){
+            rtc_found = PCF8563_RTC;
+            DEBUG_MSG("PCF8563 RTC found\n");
+        }
     }
     
 #ifdef RAK4630